ABSTRACT
The invasion of host red blood cells by Plasmodium falciparum merozoites is a complex process requiring multiple receptor-ligand interactions. Glycophorin A, a sialic acid-rich integral membrane protein, is an important RBC receptor for merozoites. We stably expressed glycophorin A in wild type Chinese hamster ovary (CHO) cells and in Lec 2 CHO cells which have a defect in the ability to sialylate proteins. Malaria merozoites were assessed for the ability to adhere to CHO cells that were either untransfected or expressed recombinant glycophorin A. Merozoites only adhered to wild type CHO cells and they did so irrespective of the expression of glycophorin A. These results suggest that cellular adhesion, the earliest event in the malaria invasion process, is mediated by sialic acid residues. This model system will provide valuable molecular information regarding early events in the malaria invasion process.
Subject(s)
Plasmodium falciparum/pathogenicity , Sialic Acids/metabolism , Animals , CHO Cells , Cell Adhesion/physiology , Cricetinae , Erythrocytes/parasitology , Glycophorins/genetics , Glycophorins/metabolism , Malaria, Falciparum/etiology , Malaria, Falciparum/parasitology , Plasmodium falciparum/growth & development , Plasmodium falciparum/physiology , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , TransfectionABSTRACT
Plasma membrane vesicles have been used to study a wide variety of biological events including the nature of receptor-ligand interactions and the physiology of molecular transport across membranes. Plasma membrane vesicles were chemically induced from an adherent Chinese hamster ovary cell line expressing recombinant glycophorin A, a well-studied intrinsic membrane protein of the red blood cell. They were also prepared from Chinese hamster ovary cells in suspension culture. Biochemical and immunological assays demonstrated the equivalence of glycophorin A on cell membranes and vesicles. The transfected Chinese hamster ovary cell membrane was also labeled with a highly aliphatic fluorescent cell linker. Vesicles produced by the fluorescein-labeled cells demonstrated bright surface staining of the plasma membrane. They too expressed glycophorin A biochemically and immunologically indistinguishable from cellular-based glycophorin A. Plasma membrane vesicles are non-adherent in culture and stably retain the fluorescent probe in the cell membrane. Fluorescein-labeled vesicles will be particularly useful for studying cellular interactions in which both constituents of a receptor-ligand pair are expressed on adherent cell lines. Unlabeled vesicles may also prove to be useful as soluble immunoadsorbants in both the clinical laboratory and basic science research settings.
